How do you get rid of these disgusting things?

Has anyone else been inundated with these vile grubs? I've had them two years running in my pots, loads of them, fat and up to 2 inches long. And I do mean LOTS of them: 24 found today in the space of 10 mins in one medium size pot! I've tried the chemical stuff but it clearly doesn't work: I followed instructions, but how much are you supposed to spray on? And is there any other method that works better? I gather from another site that nematodes don't work on these enormous things, only on the smaller ones....